An anterior cruciate ligament (ACL) that has ruptured and is non-repairable is generally replaced arthroscopically by a tissue graft. The tissue graft can be harvested from a portion of a patellar tendon having so called “bone blocks” at each end, and from the semitendonosis and gracilis. Alternatively, the tissue graft can be formed from synthetic materials or from a combination of synthetic and natural materials. The replacement tissue graft is implanted by securing one end of the tissue graft in a socket formed in a passage within the femur, and passing the other end of the graft through a passage formed in the tibia.